Human muscle cells, fungi and some bacteria undergo lactic acid fermentation, while yeast cells undergo alcoholic fermentation. Both processes take place in the cells' cytoplasm.
During lactic acid fermentation, glucose separates into lactic acid and adenosine triphosphate, or ATP. In alcoholic fermentation, it separates into ATP, ethyl alcohol and carbon dioxide molecules. When there is a lack of oxygen, living things trigger the fermentation process to release ATP energy to support cell functions. Food and beverage industries also use fermentation and its by-products to produce beer, wine, bread, sauerkraut and cheese. Other industries use it to treat sewage and produce hydrogen gas.